title: Dissipation of excess photosynthetic energy contributes to salinity tolerance: a comparative study of salt-tolerant Ricinus communis and salt-sensitive Jatropha curcas.
abstract: The relationships between salt tolerance and photosynthetic mechanisms of excess energy dissipation were assessed using two species that exhibit contrasting responses to salinity, Ricinus communis (tolerant) and Jatropha curcas (sensitive). The salt tolerance of R. communis was indicated by unchanged electrolyte leakage (cellular integrity) and dry weight in leaves, whereas these parameters were greatly affected in J. curcas. The leaf Na+ content was similar in both species. Photosynthesis was intensely decreased in both species, but the reduction was more pronounced in J. curcas. In this species biochemical limitations in photosynthesis were more prominent, as indicated by increased C(i) values and decreased Rubisco activity. Salinity decreased both the V(cmax) (in vivo Rubisco activity) and J(max) (maximum electron transport rate) more significantly in J. curcas. The higher tolerance in R. communis was positively associated with higher photorespiratory activity, nitrate assimilation and higher cyclic electron flow. The high activity of these alternative electron sinks in R. communis was closely associated with a more efficient photoprotection mechanism. In conclusion, salt tolerance in R. communis, compared with J. curcas, is related to higher electron partitioning from the photosynthetic electron transport chain to alternative sinks.
authors.affiliation: Departamento de Bioquímica e Biologia Molecular/INCTsal-CNPq/MCT, Laboratório de Metabolismo de Plantas, Universidade Federal do Ceará, CP 6004, CEP 60455-970 Fortaleza, Ceará, Brazil.
authors.forename: Milton C
authors.initials: MC
authors.lastname: Lima Neto
authors.forename: Ana K M
authors.initials: AK
authors.lastname: Lobo
authors.forename: Marcio O
authors.initials: MO
authors.lastname: Martins
authors.forename: Adilton V
authors.initials: AV
authors.lastname: Fontenele
authors.forename: Joaquim Albenisio G
authors.initials: JA
authors.lastname: Silveira
mesh_terms: D000429:Alcohol Oxidoreductases / Q000378:metabolism; D000641:Ammonia / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D019069:Cell Respiration; D002734:Chlorophyll / Q000378:metabolism; D004579:Electron Transport; D005974:Glutamate-Ammonia Ligase / Q000235:genetics / Q000378:metabolism; D031286:Jatropha / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D008027:Light; D050901:Nitrate Reductase / Q000235:genetics / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism*; D010788:Photosynthesis; D018515:Plant Leaves / Q000502:physiology; D010940:Plant Proteins / Q000378:metabolism; D018526:Plant Transpiration; D012278:Ricinus / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D055049:Salt Tolerance; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological; D014867:Water / Q000502:physiology
chemical_list: D009566:Nitrates; D010940:Plant Proteins; D014867:Water; D002734:Chlorophyll; D012965:Sodium Chloride; D000641:Ammonia; D000429:Alcohol Oxidoreductases; C020821:glycollate oxidase; D002374:Catalase; D050901:Nitrate Reductase; D005974:Glutamate-Ammonia Ligase
keywords: Castor bean; Photoprotection; Photosynthesis; Physic nut; Salt stress